1. Field of the Invention
The invention relates to a navigation system that searches various information such as route information and facility information and the like. More particularly, the invention relates to a navigation system in which search conditions can be easily set.
2. Description of the Related Art
Japanese Patent Application Publication No. 1-138409 (JP-A-1-138409), for example, describes an on-board navigation system which makes it possible to flexibly set search conditions for searching for the best route, e.g., the shortest route (i.e., giving priority to distance) or the fastest route (i.e., giving priority to estimated driving time), for a driver.
When searching for the shortest route, this on-board navigation system adds up distance data for all of the road segments in each route, and selects the route with the smallest total distance data as the preferred route.
Also, when searching for the fastest route, this on-board navigation system adds up estimated driving time data for all of the road segments in each route, and selects the route with the smallest total estimated driving time data as the preferred route.
Further, this on-board navigation system can also search for the best route taking into account both estimated driving time and distance by combining the distance data and the estimated driving time data for all of the road segments in each route, and then select the route with the smallest total cumulative data as the preferred route.
More specifically, the value of a distance coefficient (i.e., a weighting coefficient that is multiplied by each distance data when adding up the distance data) and/or a time coefficient (i.e., a weighting coefficient that is multiplied by each estimated driving time data when adding up the estimated driving time data) is set according to each search condition. For example, when the search conditions give priority to the shortest distance regardless of the estimated driving time, the distance coefficient is increased and the time coefficient is decreased so that the influence from the distance coefficient becomes relatively large with respect to the inclusive sum, and the preferred route having the smallest inclusive sum is then selected.
However, with the on-board navigation system described in JP-A-1-138409, when setting the value of the distance coefficient and the value of the time coefficient for each search condition, those values need to be entered separately. This makes the preparation until an operator can start searching for the preferred route cumbersome. It also makes it difficult for the system to handle frequent requests to change search conditions.